The overall objective of this project is to increase our understanding of the interaction of ultrasound with tissue. Two complementary approaches are taken: (a) From studies of the acoustic properties of tissues, physical processes and effects can be deduced. (b) From direct observations of biological effects we can postulate and test for the responsible mechanisms. Our specific goals for the coming year include (1) Definition and exploration of nonlinear absorption phenomena. (2) Testing of the cavitation hypothesis for the effects of ultrasound on plant roots. (3) Location of the site of action of sound in plant roots. (4) Determination whether it is possible to produce metastasis by exposure of tumors to intense ultrasound. (5) Use of Drosophila to study effects of sound on growth and development of animal tissue. (6) Test of reports of the effectiveness of ultrasound as a male contraceptive. BIBLIOGRAPHIC REFERENCES: "Problems with Absorption Measurements of Inhomogeneous Solids," by Peter W. Marcus and Edwin L. Carstensen, J. Acoust. Soc. Am., 58:1334-1335, 1975. "Dielectric Properties of Sephadex and its Water of Hydration," by George T. Koide and Edwin L. Carstensen, J. Phys. Chem. 80:55-59, 1976.